Like all Americans, I was taught that the U.S. dropped nuclear bombs on Hiroshima and Nagasaki in order to end WWII and save both American and Japanese lives.

But most of the top American military officials at the time said otherwise.

The U.S. Strategic Bombing Survey group, assigned by President Truman to study the air attacks on Japan, produced a report in July of 1946 that concluded (52-56):

"Based on a detailed investigation of all the facts and supported by the testimony of the surviving Japanese leaders involved, it is the Surveyâ€™s opinion that certainly prior to 31 December 1945 and in all probability prior to 1 November 1945, Japan would have surrendered even if the atomic bombs had not been dropped, even if Russia had not entered the war, and even if no invasion had been planned or contemplated."

General (and later president) Dwight Eisenhower â€“ then Supreme Commander of all Allied Forces, and the officer who created most of Americaâ€™s WWII military plans for Europe and Japan â€“ said:

The Japanese were ready to surrender and it wasnâ€™t necessary to hit them with that awful thing.

Newsweek, 11/11/63, Ike on Ike

Eisenhower also noted (pg. 380):

In [July] 1945â€¦ Secretary of War Stimson, visiting my headquarters in Germany, informed me that our government was preparing to drop an atomic bomb on Japan. I was one of those who felt that there were a number of cogent reasons to question the wisdom of such an act. â€¦the Secretary, upon giving me the news of the successful bomb test in New Mexico, and of the plan for using it, asked for my reaction, apparently expecting a vigorous assent.

During his recitation of the relevant facts, I had been conscious of a feeling of depression and so I voiced to him my grave misgivings, first on the basis of my belief that Japan was already defeated and that dropping the bomb was completely unnecessary, and secondly because I thought that our country should avoid shocking world opinion by the use of a weapon whose employment was, I thought, no longer mandatory as a measure to save American lives. It was my belief that Japan was, at that very moment, seeking some way to surrender with a minimum loss of â€˜faceâ€™. The Secretary was deeply perturbed by my attitudeâ€¦.

Admiral William Leahy â€“ the highest ranking member of the U.S. military from 1942 until retiring in 1949, who was the first de facto Chairman of the Joint Chiefs of Staff, and who was at the center of all major American military decisions in World War II â€“ wrote (pg. 441):

It is my opinion that the use of this barbarous weapon at Hiroshima and Nagasaki was of no material assistance in our war against Japan. The Japanese were already defeated and ready to surrender because of the effective sea blockade and the successful bombing with conventional weapons.

The lethal possibilities of atomic warfare in the future are frightening. My own feeling was that in being the first to use it, we had adopted an ethical standard common to the barbarians of the Dark Ages. I was not taught to make war in that fashion, and wars cannot be won by destroying women and children.

MacArthurâ€™s views about the decision to drop the atomic bomb on Hiroshima and Nagasaki were starkly different from what the general public supposed â€¦. When I asked General MacArthur about the decision to drop the bomb, I was surprised to learn he had not even been consulted. What, I asked, would his advice have been? He replied that he saw no military justification for the dropping of the bomb. The war might have ended weeks earlier, he said, if the United States had agreed, as it later did anyway, to the retention of the institution of the emperor.

Moreover (pg. 512):

The Potsdam declaration in July, demand[ed] that Japan surrender unconditionally or face â€˜prompt and utter destruction.â€™ MacArthur was appalled. He knew that the Japanese would never renounce their emperor, and that without him an orderly transition to peace would be impossible anyhow, because his people would never submit to Allied occupation unless he ordered it. Ironically, when the surrender did come, it was conditional, and the condition was a continuation of the imperial reign. Had the Generalâ€™s advice been followed, the resort to atomic weapons at Hiroshima and Nagasaki might have been unnecessary.

Similarly, Assistant Secretary of War John McLoy noted (pg. 500):
I have always felt that if, in our ultimatum to the Japanese government issued from Potsdam [in July 1945], we had referred to the retention of the emperor as a constitutional monarch and had made some reference to the reasonable accessibility of raw materials to the future Japanese government, it would have been accepted. Indeed, I believe that even in the form it was delivered, there was some disposition on the part of the Japanese to give it favorable consideration. When the war was over I arrived at this conclusion after talking with a number of Japanese officials who had been closely associated with the decision of the then Japanese government, to reject the ultimatum, as it was presented. I believe we missed the opportunity of effecting a Japanese surrender, completely satisfactory to us, without the necessity of dropping the bombs.

Under Secretary of the Navy Ralph Bird said:

I think that the Japanese were ready for peace, and they already had approached the Russians and, I think, the Swiss. And that suggestion of [giving] a warning [of the atomic bomb] was a face-saving proposition for them, and one that they could have readily accepted.

***

In my opinion, the Japanese war was really won before we ever used the atom bomb. Thus, it wouldnâ€™t have been necessary for us to disclose our nuclear position and stimulate the Russians to develop the same thing much more rapidly than they would have if we had not dropped the bomb.

If Japan ever gets nukes its more likely they would use them against China then the USA. Befor we used the nuclear weapons on Japan we had been firebombing Japnese cities doing just as much damage as we were with nuclear weapons several years. Even after the use of nuclear weapons the military almost prevented the surrender with an attempted revolt.

The lethal possibilities of atomic warfare in the future are frightening. My own feeling was that in being the first to use it, we had adopted an ethical standard common to the barbarians of the Dark Ages. I was not taught to make war in that fashion, and wars cannot be won by destroying women and children.

That's democracy. Different people/officials have different opinions or ideas on how to proceed on given situations. But I think like in other governments the head of the government gets the final decision on how to proceed (after hearing out his council). In this case I think to the mind of Pres. Truman after 4 years of continuous war and hundreds of thousands of American lives lost (and after seeing the carnage at Iwo Jima) he was of the honest opinion that no more American life should be wasted in forcing Japan (who at that time was understandably considered as barbaric) to surrender when there was already a weapon that can make that happen without putting anymore American lives at risk (which caused the American taxpayers millions of dollars to build).

Tell me Kunal, if you were in the shoes of Pres. Truman at that time and you were faced with the no small task of deciding to drop the bombs over Japanese cities, would you take the route that we know now or would you have preferred instead to send hundreds of thousands of young Americans to invade mainland Japan - into certain death for a lot of them? In my case, I'd do what Pres. Truman did.

BTW, we don't know what motivated the officials you quoted above in making those statements. For all we know they had personal or professional differences with Pres. Truman that they were venting out by uttering those statements or taking those positions vis-a-vis the dropping of atom bombs against Japanese cities. I know for a fact that Gen. Eisenhower was the political enemy of Pres. Truman.

It was necessary to use that.Not only to save American lives also Japanese lives.

There were three alternatives to the Atomic bombing of Japan with itâ€™s attendant 200,000 (approx) casualties
Firstly, hold off on the Nukes and bomb the Japanese into submission using conventional bombs. Remember that 120,000 people died in one raid on Tokyo(Tokyo fire bombing) and it appeared to have no effect on the Japanese will to continue fighting.

Secondly, invade the Japanese home islands where the civilian population were being trained to take on the invaders with carving knives attached to broom handles,as well as new volunteer force was made.
The estimates for casualties, based on what happened on Iwo Zima,Okinawa and Saipan.Remember in these 3 islands,considered Japanese home land,Japanese soldiers fought to death,even there were many hide outs of Japanese soldiers who did not surrender.There US marines and Army had to fight a lot.
And also any one should not forget land based Kamikazes,they resulted heavy damage on US navy in Okinawa and Iwo Zima,by August Japanese invented "Okha" suicide crafts,it could carry 1200 KG bomb,it was far better than normal aircrafts that Japan used for Kamikazes.
Zero plane,attached with 250 Kg bomb,it was easy to shoot down,as it lacked armour.
Same to other planes,Japanese pilots by 1945 was ill trained than Americans,most of the Kamikazes were shot down on way by US fighter or anti-aircraft guns.But Okha was very fast.

Thirdly, to starve them out.
Blockade the Japanese home ports whilst continuing the ground war in China-Burma-India and wait for them to drop from exhaustion. Sounds great doesnâ€™t it? Minimal casualties, no-one killed by iron or atomic bombs falling from the sky, everyone happy to see the end of the war. Letâ€™s look at the likely final scenario.
After the war had been won in 1946 or 7 with the pitiful sight of the last Japanese soldiers dropping from starvation on the home islands, and the inevitable pictures taken as the victorious Allied soldiers marched through a country blighted by the death of 90% of itâ€™s civilian population, bodies putrefying and unburied on the streets, dysentery, cholera and various other diseases rampant among the few remaining lucky survivors, how long would it have been before the Bleeding Heart Liberals started comparing Truman to Hitler and claiming that he had treated the Japanese as bad as Germany had treated the Jews by locking them up and giving them no means of sustenance?
And then when it turns out that he had a bomb that would have shown the might of the USA to the world and maybe one or two of them dropped on strategic towns may have forced the Japanese to surrender early and forgo the horrors of 2 years of starvation. OH MY, he would have been pilloried.
So which of the 4 possible methods would you have chosen? Would you have the brass cojones necessary to pick the one with the least total casualties?

So it seems atomic bombing was right according to contemporary situation.Also US warned Japan,that if Japan would not surrender,they(US) would use a new very powerful,and leaflets were also dropped,still Japanese decided to continue war.
Even after drop of atom bombs,some Japanese Generals decided to continue fighting.

There are voices which assert that the bomb should never have been used at all. I cannot associate myself with such ideas. . . . I am surprised that very worthy peopleâ€”but people who in most cases had no intention of proceeding to the Japanese front themselvesâ€”should adopt the position that rather than throw this bomb, we should have sacrificed a million American and a quarter of a million British lives. . . .
:Winston Churchill, leader of the Opposition, in a speech to the British House of Commons, August 1945[7]

The U.S. military had nearly 500,000 Purple Heart medals manufactured in anticipation of potential casualties from the planned invasion of Japan.

According to historian Richard B. Frank,

"The intercepts of Japanese Imperial Army and Navy messages disclosed without exception that Japan's armed forces were determined to fight a final Armageddon battle in the homeland against an Allied invasion. The Japanese called this strategy Ketsu Go (Operation Decisive). It was founded on the premise that American morale was brittle and could be shattered by heavy losses in the initial invasion. American politicians would then gladly negotiate an end to the war far more generous than unconditional surrender.

"also hoped that if they could hold out until the ground invasion of Japan began, they would be able to inflict so many casualties on the Allies that Japan still might win some sort of negotiated settlement.